Tunable cavity resonator



March 1, 1949. RECQRD I 2,463,423

TUNABLE CAVITY RESONATOR Filed Dec. 17, 1945 'INVENTOR. 24 FRANK A. RECQRD ATTORNEY Patented Mar. 1, 1949 TUNABLE CAVITY RESONATOR Frank A. Record, Potsdam, N. Y., assignor to the United States of America as represented by the Secretary of War Application December 17, 1945, Serial No. 635,586

5 Claims. 1

This invention relates generally to electrical apparatus and more particularly to tunable cavity resonators.

In one type of tunable cavity resonator known to the prior art to which the case belongs, threaded plugs are used to vary the resonant frequency of the cavity. In this method, tuning is some times cumbersome and the frequency range may be limited.

It is an object, therefore, of this invention to provide a cavity resonator which may be conveniently tuned over a selected band of frequencies without these disadvantages.

It is a further object of this invention to provide a cavity resonator which may be tuned continuously over a relatively wide band of frequencies.

In general, this invention comprises a cavity resonator in the shape of a right elliptical cylinder having a longitudinal fold in each of the bases which will permit the physical dimensions and hence resonant frequency of the cavity to be varied by the application of a transverse compressive force at the side walls of the cavity.

Other objects, features, and advantages of this invention will suggest themselves to those skilled in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawing in which:

Fig. 1 is a side view of the cavity resonator;

Fig. 2 is a top view of the same; and

Fig. 3 is an end view of the same.

Referring now to the drawings, the invention comprises a cavity resonator of a right elliptical cylindrical form. The bases Ii and 52 of the structure are made of a metal such as oxygen free high conductivity copper, and the elliptical perimeter strip l3 as illustrated in Fig. 2 is made of a metal such as phospher bronze. major axis of each base (I I and I2) there is an extruded longitudinal fold (l4 and I5) as illustrated in Fig. 3, which extend-s only between the foci (i6 and H) of the bases (H and i2). Two slits l8 and IS) in each base are cut perpendicular to the folds (l4 and I5) and pass through the foci (l6 and II).

The slits (l8 and l'9) separate the end pieces (25 and 2!) from the center section 22. On the exterior of the sides of the cavity, steel members (23 and 24) are arranged in such a way that a transverse compressive force can be applied to the cavity. Input radio frequency power may be supplied to the resonator by means of a loop of copper wire 25 inserted through one end of the Along the spring-like quality of the center sections.

structure or by any other convenient and well known means. The output of the resonator may be obtained from a similar loop 26 at the opposite end of the major elliptical axis. The height of the structure should be less than one-half wave length at the desired resonant frequency.

In operation, tuning is accomplished by applying from a convenient source a transverse compressive force to two members (23 and 24) along the side Walls of the cavity. Any increase in pressure on the members (23 and 24) will cause the folds (l4 and 15) to deepen and the center adjustable section to become smaller thereby causing the resonant frequency to increase. A decrease in pressure will cause the folds (l4 and IE) to decrease in depth and permit the center section to become larger and thereby causing the resonant frequency to decrease. The resiliency of the sidewalls, which are made of a metal such as phospher bronze, accounts for the Because the end pieces (20 and 2|) are separated from the adjustable center section by slits (l3 and I9), they do not change in shape.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention, and accordingly I claim all such departures as fall fairly within the spirit and scope of the hereinafter appended claims.

What is claimed is:

1. In a tunable cavity resonator, a resonant cavity in the shape of a right elliptical cylinder, the bases of said cavity being formed by high conductivity copper, an elliptical perimeter strip made of a metal such as phospher bronze, said bases being constructed in such a manner that there is an extruded longitudinal fold in each of the said bases, said folds extending only between the foci of the said bases, two transverse slits in each of said bases, said slits passing through the foci of each of said bases, and means cooperating with the side walls of said cavity and adapted to change the parameters of the cavity during the application of force to said means.

2. A tunable cavity resonator comprising an elliptical cylindrical wall and two right sections enclosing upper and lower ends thereof, said ends having transverse slits at the foci thereof and a longitudinal extrusion extending between said foci, whereby said cavity may be tuned by thev application of compressive forces to the cylindrical wall thereof.

3. A tunable cavity resonator comprising an enclosing wall and two right sections closing the upper and lower ends thereof, each of said sections having two parallel transverse slits extending thereacross at right angles to a major axis and an extrusion extending between said slits whereby said cavity may be tuned by the application of Compressive forces to the enclosing wall thereof.

4. A tunable cavity resonator comprising an elliptical cylindrical wall and two right sections enclosing upper and lower ends thereof, each of said ends having a transverse slit at each focus, said slits being parallel to each other, said end sections having an extrusion extending between said slits, whereby said cavity may be tuned by the application of compressive forces to said cylindrical wall.

5. A tunable cavity resonator comprising an 4 elliptical cylindrical wall and two right sections enclosing upper and lower ends thereof, each of said ends having transverse slits at the foci thereof, said end sections having a longitudinal extrusion extending between said foci, said slits being parallel to each other and perpendicular to said extrusion whereby said cavity may be tuned by the application of compressive forces to the cylindrical wall thereof.

FRANK A. RECORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,356,414 Linder Aug. 22, 1944 2,357,313 Carter Sept. 5, 1944 2,409,321 Stephan Oct. 15, 1946 2,428,037 Roberts Sept. 30, 1947 

